M86.231
BillableSubacute osteomyelitis, right radius and ulna
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.231 an HCC code?
Yes. M86.231 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for M86.231
For M86.231to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M86.231 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.231 is the ICD-10-CM diagnosis code for subacute osteomyelitis, right radius and ulna. A bone infection in the right forearm bones (radius and ulna) that develops gradually over weeks to months, causing inflammation and potential bone damage. M86.231 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering other osteopathies (m86-m90).
Under the CMS-HCC V28 risk adjustment model, M86.231 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, M86.231 mapped to the same category but with a base RAF weight of 0.482 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Confirm that both or either of the forearm bones are involved and document which specific bone(s) are affected. Because M86.231 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M86.231 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm that both or either of the forearm bones are involved and document which specific bone(s) are affected
- •Verify right side laterality is clearly stated in the clinical documentation
Clinical Significance
Subacute osteomyelitis of the right radius and ulna represents a complex dual-bone infection with gradual onset in the forearm over weeks to months. This condition affects both forearm bones simultaneously, requiring comprehensive treatment to preserve forearm rotation and hand function.
Documentation Requirements
- ✓Specific documentation of right radius and ulna involvement
- ✓Evidence of subacute infection timeline
- ✓Clinical signs of dual forearm bone infection
- ✓Imaging confirmation of both radius and ulna involvement
- ✓Laboratory evidence of ongoing bone infection
- ✓Assessment of forearm rotation and hand function
- ✓Documentation of symptom progression over time
- ✓Treatment plan addressing dual bone involvement
Commonly Confused Codes
- •M86131 — Other acute osteomyelitis of right radius and ulna
- •M86631 — Chronic osteomyelitis with draining sinus of right radius and ulna
- •M86331 — Chronic multifocal osteomyelitis of right radius and ulna
- •S52.91XA — Unspecified fracture of right forearm
- •M25531 — Pain in right wrist